Production of O2(1Σ +g) in the H + O2 system

Abstract

Chemiluminescence is observed in the reaction between atomic hydrogen and molecular oxygen. Bands at λ= 1265, 1430 and 1510 nm are ascribed to transitions involving HO₂, while that at λ= 762 nm is due to the O₂(¹Σ⁺_g→³Σ^–_g) transition. Evidence is adduced to show that O₂(¹Σ⁺_g) is not produced by energy-pooling from O₂(¹Δ_g), and that O₂(¹Δ_g) is itself only a minor contributor to the band at λ= 1265 nm.

The bands at λ= 762 and λ= 1430 nm both show a first order dependence on [H] and on [O₂]. We examine several reactions which are possible sources of O₂(¹Σ⁺_g) and conclude on the basis of the kinetic evidence, that the most probable reaction sequence is H + O₂+ M → HO₂+ M (4), H + HO₂→ H₂+ O₂(¹Σ⁺_g). (6c′)

Measurement of absolute concentrations of H and O₂(¹Σ⁺_g) allows estimation of the efficiency of reaction (6c′) relative to the overall loss of HO₂ in reaction (6) H + HO₂→ products. (6) The value obtained for the efficiency is 2.8 ± 1.3 × 10^–4, so that ∼10^–3 of the molecular oxygen formed in the reaction is in the ¹Σ⁺_g state.

Alternative excitation mechanisms are also assessed.